It makes more sense if you think of a production like AGT less as the reality show it pretends to be, and more as a promotional reel for labels.
Of course the content they choose to promote is indexed.
> Alphonso's software uses the same technology that Shazam and similar services employ to automatically detect the song you're listening to. It samples small bits of audio, creating a digital "fingerprint" of it, and comparing it against a a database on their server to identify the show or movie. In fact, Alphonso's CEO says they have a deal with Shazam, and use their specific technology to do this. But this embedded software can even be listening even when your phone's screen is turned off and it's ostensibly idle.